Biology Science of life and living organisms Greek words: “Bios” = life “Logos” = study Branches of Biology Top 3 Main Branches: Zoology Botany Microbiology Anatomy ➔ Deals with the study of the structure of organisms and their parts Biochemistry ➔ Concerned with the chemical and physicochemical processes that occur within living organisms Biophysics ➔ Application of the laws of physics to biological phenomena Biotechnology ➔ Exploitation of biological processes such as genetic manipulation of micro-organisms for the production of antibiotics, hormones, etc. Botany ➔ Scientific study of plants (structure, physiology, genetics, and ecology) Cell Biology ➔ Study of the cell structure and function ➔ Revolves around the concept that the cell is the basic unit of life Evolution ➔ Process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during Earth;s history (Darwinism) Genetics ➔ Study of genes, genetic variations, and heredity Immunology ➔ Concerned with immunity Marine Biology ➔ Study of organisms in the ocean or other marine bodies of water Microbiology ➔ Study of microscopic organisms (unicellular, multicellular, or acellular) Molecular Biology ➔ Deals with the structure and function of the proteins and nucleic acids Mycology ➔ Study of fungi Parasitology ➔ Study of parasitic organisms Photobiology ➔ Study of the interactions of light and living organisms Phycology ➔ Study of algae Physiology ➔ Deals with the normal functions of living organisms and their parts Cytology ➔ Study of form and structure of cells (behavior of nucleus and other organelles) Plant Physiology ➔ Sub-discipline of botany ➔ Physiology (functioning) of plants Ecology ➔ Deals with relations of organisms to one another and to their physical surroundings Radio Biology ➔ Study of the action of ionizing radiation on living things Structural Biology ➔ Branch of molecular bio, biochem, and biophysics dealing with the molecular structure of biological macromolecules Taxonomy ➔ Science of identification, nomenclature, and classifications of organisms Theoretical Biology ➔ Mathematical biology ➔ Interdisciplinary scientific research field with applications in bio, biotech, and medicine Reproduction ➔ When reproduction occurs, genes containing DNA are passed along to an organism’s offspring ➔ These genes ensure that the offspring will be of the same species and will have similar characteristics Single-celled Organisms ● First duplicates their DNA ● Then divides it equally as the cell prepared to divide to form 2 new cells Virology ➔ Study of viruses Multicellular Organisms ● Produce specialized reproductive germline cells that will form new individuals Zoology ➔ Study of the behavior, structure, physiology, classification, and distribution of animals Growth and Development ➔ Organisms grow and develop following instructions coded by their genes Characteristics of Life Genes ● Order ➔ This is what defines “life” Organisms are highly organized Single-celled Organisms ● Atoms make up molecules that make up cell organelles and other cellular inclusions Multicellular Organisms ● Form tissues that in turn, collaborate to create organs ● Organs work to form organ systems Sensitivity or Response to Stimuli ➔ Organisms respond to diverse stimuli ➔ Even tiny bacterias can move towards or away from chemicals (chemotaxis) or light (phototaxis) ➔ Movement towards stimulus = positive response ➔ Movement away from stimulus = negative response Example: ❏ Plants bending towards a source of light or respond to touch Provide instructions that will direct cellular growth and development Regulation ➔ Even small organisms are complex and require multiple regulatory mechanisms for coordinating internal functions, response to stimuli, and cope with environmental stress Example: Internal functions regulated in an organism ❏ Nutrient transport and blood flow ❏ Organs performing specific functions like: Carrying oxygen Removing wastes Delivering nutrients Cooling the body Organs ● Group of tissues working together Homeostasis (steady state) ➔ Ability of an organism to maintain constant internal conditions despite environmental changes Parts: Example: ❏ An organism needs to regulate body temperature through thermoregulation ❏ Polar bears and other organisms living in cold climates have body structures that helps them withstand low temperatures and conserve body heat: Fur Feathers Blubber Fat ❏ In warm climates, organisms have methods (like perspiration) to help shed excess body heat Energy Processing ➔ All organisms use a source of energy for their metabolic activities ➔ Some organisms capture energy from the sun = chemical energy in food (photosynthesis) ➔ Other use chemical energy in molecules as food (cellular respiration) 1. 2. Nucleoid ● Genetic material ● Continuous, circular DNA molecule that lies free in the cell Cell Wall ● Rigid, protects ● Composed of peptidoglycan Peptidoglycan Unicellular Gives strength to the outer structure of organism Forms cell walls by cross-linking between amino acids that produces a strong mesh-like structure Consisting of glycosaminoglycan chains interlinked with short peptides Unicellular ➢ Single cell Multicellular ➢ Many great cells that work together Cells - Basic unit of life Smallest unit that can carry out necessary life activities Different types of cells (2) Prokaryotic Cells ➔ Smaller than eukaryotic ➔ No nucleus and membrane-bound organelles Examples: ❏ Bacteria ❏ Archaebacteria ❏ Rickettsiae 3. Cell Membrane ● Regulates passage of materials in and out of the cytoplasm ● Thin membrane pushed up against the inner surface of the prokaryotic cell ● Composed of 2 layers: ❏ Flexible lipid molecules ❏ Durable proteins (interspersed in lipid molecules) that is both supple and strong ● Selectively permeable ❏ Allows only certain substances to pass through ● Separates the cell’s contents from its surrounding fluids 4. 5. Cytoplasm ● Semi-fluid that fills the cell (65% water) ● Enclosed in plasma membrane ● Billion molecules per cell ● Storehouse that includes enzymes and dissolved nutrients (sugars and amino acids) ● Contains DNA (deoxyribonucleic) Ribosomes ● The protein factory ● Carry out protein synthesis ● Only organelles in prokaryotic cells ● Chum out proteins to: Provide needed enzymes Replace worn-out transport proteins Provide other proteins required 6. Pilus or Pili ● Extends out of the cell to transfer DNA to other bacterium 7. Flagellum / Flagella ● A long fiber that helps them move (for locomotion) 8. Plasmid ● Small chromosome with extra genes 9. Capsule ● Sticky substance external to the cell wall ● Protects bacteria from white blood cells 10. Mesosomes ● Artifacts created when cells are prepared for viewing with electron microscopes Additional Information: Prokaryotic ❖ Can be rod-like, spherical, or spiral ❖ Lives in a watery environment ❖ Tiny pores on cell walls allows water and other substances dissolved in it (like oxygen) to flow into the cell and allow wastes to flow out Eukaryotic Cells ➔ Contains membrane-bound structures nucleus and cytoplasm ➔ Filled with tiny structures called organelles Examples: ❏ Animal Cell ❏ Plant Cell The Eukaryotic Animal Cell ➔ About 10 times larger than prokaryotic ➔ No cell walls ➔ Contains organelles Parts: 1. The Nucleus ● Directs activities of the cell ● Carries the genetic information ; had numerous strands of DNA The length is many times the diameter of the cell ● ● ● Largest organelle Contains chromosomes Genetic information Responsible for the cell’s ability to reproduce Other parts: ★ Nuclear Envelope Double layered membrane that separates the nucleus from the cytoplasm ★ Nucleolus Where rRna is made and ribosomes are assembled ★ Nucleoplasm Cellular material Sticky liquid that supports the chromosomes and nucleoli For suspension of organelles inside the nucleus ★ Nuclear Pores Allow the exchange of cellular materials between the nucleoplasm and the cytoplasm 2. Plasma Membrane ● Outer envelope that surrounds eukaryotic cells ● Double-layered structure of phospholipid molecules interspersed with cholesterol and proteins ● Has phospholipids a. Hydrophobic fatty acid tails Hates water Faces inward b. Hydrophilic phosphate heads Loves water Faces outward ● Regulates movement of substances in and out of the cell ● Semi-permeable Only certain substances (namely proteins) can pass through unaided Tiny gaps in the membrane enable small molecules (like water) to diffuse readily in and out of the cell. 3. Ribosomes ● Protein manufacturer of all proteins requires by the cell or secreted by it ● Sites of protein synthesis ● Round structures composed of RNA and proteins ● Can be floating in the cytoplasm or bound to the Rough Endoplasmic Reticulum ● Works with other molecules 4. Endoplasmic Reticulum ● Elongated membranous sac attached to many regions of the cytoplasm (nuclear membrane) Rough Endoplasmic Reticulum Filled with ribosomes Help assemble proteins that typically are exported from the cell Synthesis of membrane proteins, secretory proteins, and hydrolytic enzymes and formation of transport vehicles Smooth Endoplasmic Reticulum Lipid synthesis, hormones, steroids Carbohydrate metabolism in liver cells Detoxification in liver cells and calcium ion storage ★ Break toxic chemicals down No ribosomes - - 5. Contains enzymes needed for the construction of molecules (carbohydrates and lipids) Prominent in liver cells (detoxification of substances) Golgi Bodies / Apparatus ● Looks like stacks of flattened sacs ● Packed with enzymes that process proteins It adds sulfur or phosphorus atoms to certain regions of the protein or chop off tiny pieces from their ends ● Modify, process, and sorts products ● “Packaging’ and “distribution” centers for materials to be shipped out of the cell The Signal Group of 4 to 100 amino acids acquired during the protein’s assembly on ribosomes Molecular shipping label to direct protein to its proper location 6. Mitochondria ● Powerhouse of the cell ● Enzymes convert sugar glucose and other nutrients into Adenosine Triphosphate (ATP) ● Contains their own DNA ● Have their own ribosomes ● Divide independently of the cell Adenosine Triphosphate (ATP) Most production is on cristae (folds in the inner mitochondrial membrane) Energy battery for countless processes: ★ Shuttling of substances across the plasma membrane ★ Building and transport of proteins and lipids ★ Recycling of molecules and organelles ★ Dividing of cells 7. Lysosomes ● Recycling center and garbage disposal (proteins, lipids, and other molecules) ● Carry digestive enzymes that: Breaks down old, worn-out organelles, debris, or large ingested particles / organelles Ship those particles’ building blocks to the cytoplasm that are used to construct new organelles 8. Centrioles (not found in plant cells) ● Small, paired, cylindrical structures found within microtubule organizing centers (MTOCs) ● Most active during cellular division ● Produces microtubules which pull the replicated chromosomes apart and move them to opposite ends of the cell when it is ready for division 9. Vacuoles ● Empty cavity = Latin of “vacuole” ● Fluid-filled sacs that stores water, food, wastes, salts, or pigments 10. Peroxisomes ● Detoxifies various substances (producing hydrogen as a by product) ● Contain enzymes that break down hydrogen peroxide into oxygen and water ● In animals, they are common in the liver and kidney cells 11. Cytoskeleton ● Dynamic network of protein tubules, filaments, and fibers ● Crisscrosses the cytoplasm, anchoring the organelles in place ● Provides shape and structure ● Many components of this are assembled / disassembled by the cell as needed During cell division, a spindle is built to move chromosomes around. After cell division, the spindle is dismantled as it is no longer needed. Most Important Fibers: a. Microtubules Made up of tubulin Participate in cellular division and movement Integral part of: ★ Centrioles ★ Cilia and flagella b. Microfilaments Some components of this are like microscopic tracks along which proteins and other molecules travel like mini trains Chlorophyll Light capturing pigment that gives plants their green color 2. Central Vacuole ● Big, takes up a huge space in the cytoplasm ● Stores water, salts, sugar, proteins, and other nutrients ● Stores the pigments (red, blue, purple) that give flowers their colors ● Contains plant wastes that tastes bitter to some insects = won’t feast on the plant ● Contains the cell sap 3. Cell Wall ● Surrounds and protects the plasma membrane (made of cellulose) ; rigid layer ● Its pores enables materials to go in and out of the cell ● The strength of this wall enables cell to absorb water into the central vacuole and swell without bursting ● Found in plants, fungi (made of chitin) and bacteria Example of Animal Cells: ❏ Euglena ❏ Paramecium The Eukaryotic Plant Cell ➔ Have all the component of animal cells ➔ But has additional structures unique to plant cells only Chitin - Principle component of an artrhopod’s exoskeleton Fibrous substance consisting of polysaccharides As the cell wall absorbs water to the vacuole, it creates water pressure that provides plants with rigidity. Without it, the cells collapse and the plant wilts. Summary Additional Parts: 1. Chloroplasts ● Convert light energy into sugar glucose (by photosynthesis) ● Possess a circular chromosome and prokaryotic-like ribosomes ● Contains the chlorophyll Structure Prokaryote Plant Animal Cell Wall Yes Yes No Plasma Membrane Yes Yes Yes Organelles No Yes Yes Nucleus No Yes Yes Centrioles No No Yes Ribosomes Yes Yes Yes Chloroplast No Yes No Chromosomes Single circular Multiple double helix Multiple double helix Vacuole No Yes No Lysosomes No No Yes Cell Theory - Scientific theory that all living organisms are made of cells as the smallest functional unit History ● Antony van Leeuwenhoek created a microscope in the 1600s. He observed the movements of protista (single-celled organism) and sperm which he termed “animalcules” ● Robert Hooke coined the term “cell” in 1665 for the box-like structures he observed when viewing a cork tissue through a lens ● In 1670s, van Leeuwenhoek discovered bacteria and protozoa ● Botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory Unified Cell Theory ➔ The cell is the fundamental unit of structure and function in living things ➔ All organisms are made up of one or more cells ➔ Cells arise from preexisting cells through cellular division Schleiden and Schwann proposed spontaneous generation (abiogenesis) a s a method of cell origination but was later disproved Rudolf Ludwig Karl Virchow ● Postulated the idea of “Omnis cellula e cellula” = all cells only arise from preexisting cells Cell Types Epithelial Cells ➔ Tightly attached to one another ➔ Cover ove interior of hollow organs (blood vessels or digestive organs) or form the surface of things (skin) ➔ Without this, we would have no skin to protect our body and would probably have no stomach too Nerve Cells ➔ Specialized for communication ➔ Send signals from the brain to muscles and glands that control their function ➔ Receive sensory information to the brain ➔ Without this, we would have no consciousness or control over our body Muscle Cells ➔ Specialized for contraction ➔ Helps us move ➔ Three kinds: Pull and tug on bones and tendons to produce motion Form thick outer walls of hollow organs Contracts to regulate the diameter of hollow organs Connective Tissue Cells ➔ Provide structural strength to the body ➔ Defends the body against foreign invaders (bacteria) ➔ Two types: fibroblasts and fat cells (native to connective tissue) ➔ Other cells goes here from the bloodstream to fight diseases ➔ Special types: cartilage and bone - designed to be stronger and more rigid Cell Modification - Specialized or modifications re-acquired by the cell after cell division that helps the cell in many ways Apical Modification ➔ Cell modification found on the apical surface of the cell Apical Surface Surface of the epithelial cell that is exposed to the exterior environment Villi ❏ ❏ Finger-like projections that arise from epithelial layer in some organs Help increase surface area allowing for faster and more efficient absorption Microvilli ❏ Smaller projections that arise from the cell’s surface ❏ Also increase surface area allowing faster and more efficient absorption Pseudopods ❏ Temporary, irregular loves formed by amoebas and some other eukaryotic cells ❏ Bulge outward to move the cell / engulf prey ExtraCellular Matrix (ECM) ❏ Compound secreted by the cell on its apical surface ❏ Cell wall is the extracellular structure in plants ❏ Glycoprotein is the main ingredient of ECM in animal cells Basal Modification ➔ Cell modification found on the basal surface of the cell Examples: Basal Surface Bottom edge of the cell Cilia and Flagella ❏ Cilia are short, hair-like structures that move in waves ❏ Flagella are long whiplike structures ❏ Formed from microtubules Example: Desmosomes / Hemidesmosomes ❏ Anchoring junction on the basal surface of the cell ❏ Rivet-like links between cytoskeleton and extracellular matrix components ❏ Primarily composed of keratin, integrins, and cadherins Lateral Modification ➔ Cell modification found on the basal surface of the cell Gap Junction ❏ Communicating junctions ❏ Closable channel that connect the cytoplasm of adjoining animal cells ❏ Presence of connexon that allow direct exchange of chemicals between the cytoplasm of 2 cells Examples: Tight Junction ❏ Act as barriers that regulate the movement of water and solutes between epithelial layers Cell Transport - Adhering Junction ❏ Anchoring junction on the lateral surface of the cell ❏ Fasten cells to one another The movement of substances across the cell membrane either in or out of the cell Cell’s phospholipid membranes are selectively permeable ❖ Has control over what molecules or ions leave or enter the cell Passive Transport ➔ Occurs when substances cross the plasma membrane without any input of energy from the cell ➔ Not energy is needed because the substances are moving from an area where they have higher concentration to an area where they have lower concentration Types of Osmosis: In a sugar solution, the solution is characterized by the solute. The more the particles of a solute, the higher the concentration. The solute particles always move from an area with higher concentration to an area with less concentration. It goes by itself without the need of extra energy Two Types: Simple Diffusion ● Defined as the net movement of molecules from an area of greater concentration to a region with lesser concentration The molecules are in constant motion due to kinetic energy, so they collide with each other causing them to divert in different directions. Over time, these molecules will be propelled to an area with lower concentration from an area with a higher one. Thus, the net movement of molecules is always from more tightly packed areas to less tightly packed areas. Concentration Agent Unequal distribution of molecules Causes a dynamic equilibrium ➢ Said to be dynamic because molecules continue to move yet there is no net change in concentrations Osmosis (under simple diffusion) ● Specific type of diffusion ● Passage of water from a region of high water concentration through a semipermeable membrane to an area of low water concentration ● Water moves in and out of the cell until equal concentration is the same on both sides of the plasma membrane Semipermeable Membranes Thin layers that allows and prevents some things to pass through An example is the cell membrane Context example - red blood cells immersed into sugar solutions: Isotonic Solution ❏ Concentration of the solute in the solution = to the concentration of solute in cells ❏ Iso = equal or the same as normal ❏ A red blood cell will retain its normal shape in this environment as the amount of water entering the cell = to the amount leaving the cell Hypertonic Solution ❏ Concentration of the solute in the solution can be greater than the concentration of solute in cells ❏ Hyper = greater than normal ❏ A red blood cell will appear to shrink as the water flows out of the cell and into the environment Hypotonic Solution ❏ Concentration of solute in the solution can be less than the concentration of solute in the cells ❏ Hypo = less than normal ❏ A red blood cell will become swollen and potentially rupture as water goes in the cell Facilitated Diffusion ➔ Diffusion with the help of transport proteins ➔ Hydrophilic molecules, charged ions, and large molecules (glucose) needs this Transport Proteins Special proteins that gives help Types of Transport Proteins Channel Proteins ❏ Form pores or tiny holes in the membrane ❏ Allows water molecules and small ions to pass through the membrane without coming into contact with hydrophobic tails Carrier Proteins ❏ Binds with specific ions / molecules and they change shape ❏ As they shift, they carry the ions / molecules across the membrane These differences in concentration create an electrical gradient across the cell membrane called cell membrane potential. Cell Membrane Potential ● Controlling this is critical for vital body functions (transmission of nerve impulses and contraction of muscles) Vesicle Transport ● Requires energy ● Usually needed by some molecules (like proteins) that are too large to pass the plasma membrane regardless of their concentration inside and outside Types Active Transport ➔ Occurs when substances are moving from an area of lower concentration to an area with higher concentration ➔ The energy comes from ATP ➔ May also require transport of proteins (such as carries proteins embedded in plasma membrane) Endocytosis ❏ Moves a substance into the cell ❏ The plasma membrane completely engulfs the substance, a vesicle pinches off from the membrane and it carries the substance into the cell Three types of Endocytosis: Phagocytosis: when an entire cell / other solid particle is engulfed Pinocytosis: when fluid is engulfed Receptor-mediated endocytosis: when the content is taken in specifically with the help of receptors on the plasma membrane Sodium-Potassium Pump ● Mechanism of active transport ● Moves sodium ions out of the cell and potassium ions into the cell (both are from areas of lower concentration so energy by the ATP is needed) ● Requires carries proteins Sodium Principal ion in the fluid outside of cells Normal sodium concentrations are about 10 times higher outside than inside Potassium Principal ion in the fluid inside of cells Normal potassium concentrations are about 30 times higher inside than outside Exocytosis ❏ Moves substance out of the cell ❏ A vesicle containing the substance moves through the cytoplasm to the cell membrane then the vesicle membrane fuses with the cell membrane and the substance is released ➔ ➔ ➔ ➔ ➔ Homeostasis Balance within the cell or a body Organism’s ability to keep a constant internal environment Requires constant adjustments because conditions always shift in and out of the cell Homeostatic Regulation ★ Adjusting of systems within a cell ★ The cellular processes above play an important role in this ★ Must be continuous to stay at or near the normal proportions in our body In a nutshell… this is Cell Transport Succession of chemical reactions that builds molecules from smaller components Requires energy (endergonic) Allows the body to grow new cells and maintain tissues Use simple chemicals and molecules to create finished products Makes polymers Classic anabolic hormones Growth Hormone Made by the pituitary gland Stimulates growth Insulin - Hormone made by the pancreas Regulates the level of sugar glucose in the blood Cells cannot utilize glucose without this Testosterone Development of male sex characteristics (deep voice, facial hair) Strengthen muscles and bones Estrogen Strengthening bone mass Development of female characteristics (breasts) Catabolism ➔ Breaking down of things ➔ Series of chemical reactions that break down complex molecules into smaller units ➔ Releases (exergonic) and provides our body with energy needed for physical activities (cellular processes to movements) ➔ Release small molecules for other purposes, detoxify chemicals, and regulate metabolic pathways Metabolism Anabolism ➔ Building up of things Catabolic reactions break down polymers into their monomers, for example: Polysaccharides to monosaccharides Starch is broken down into glucose Nucleic acids to nucleotides Nucleic acids (like those that makes up DNA) are broken down to purines, pyrimidines, and pentose sugars Involved in body’s energy supply Proteins to amino acids Protein is sometimes broken down to amino acids to make glucose When we eat, our body breaks the nutrients and that releases energy which is stored in ATP. The energy stored in ATP is the fuel for anabolic reactions. Catabolism creates the energy that anabolism consumes for: ❏ Synthesizing hormones, enzymes, sugars, other substances ❏ Cell growth ❏ Reproduction ❏ Tissue repair Photosynthesis - - Process by which green plants, algae and certain bacteria harness energy from sunlight and turn it to chemical energy (glucose) To perform photosynthesis, you need 3 main ingredients: ❖ Carbon Dioxide ❖ Water ❖ Sunlight In green plants, light energy is captured to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds. Some definitions: Autotrophs Organisms that can produce their own food Plants are autotrophs Respiration Process in which animals take in gases in the atmosphere Plants on the other hand, take in and use carbon dioxide for photosynthesis Happens in the mitochondria of the cell (with oxygen, so it is an aerobic respiration) Respiration in plants happen through a series of enzyme-driven reactions that involved sugar and the stored energy of carbohydrates produced in photosynthesis to produce energy for plant growth and metabolic processes Transpiration Process by which plants release water in the form of moisture or water vapor (evaporates) Water passes through tiny pores called stomata and other parts of plants (stems) and evaporates in the atmosphere Main function: ● Cooling the plant ● Pumping water and minerals to the leaves for photosynthesis The Photosynthetic Process What we know (basic concept) Plants need 3 requirements for photosynthesis: 1. Gases (Carbon Dioxide) ★ Coming from animals through respiration 2. Water ★ Taken through the roots of a plant 3. Light from the sun ★ The energy from the light leads to a chemical reaction that break down molecules of carbon dioxide and water that produces glucose (sugar) and oxygen gas After the production of sugar, it is broken down by the mitochondria = energy for growth and repair of plants. The oxygen is released. Formula for Photosynthesis 6CO2 + 6H2O + Light energy → C6H12O6 (sugar) + 6O2 ➢ In a nutshell, photosynthesis is a transfer of energy from the Sun to plant. ➢ What we should know (in-depth concept) There are 2 types of reactions that happens (occurs in chloroplasts) Light-dependent Reactions ● Light reactions ● When a photon of light hits the reaction center, a pigment molecule (such as chlorophyll) releases an electron ● Happens in the thylakoid ● Produces ATP and NADPH How it goes: ➢ The released electron travels through an electron transport chain (call it ETC) ➢ ETC generated the energy needed to produce ATP and NADPH ➢ The “electron hole” in the original chlorophyll pigment is filled by taking an electron from water = releasing oxygen into the atmosphere NADPH Nicotinamide Adenine Dinucleotide Phosphate Hydrogen Used to donate electrons and hydrogens to reactions catalyzed by some enzymes In other reactions, it helps carry electrons and protons given by the sunlight into new carbon-carbon bonds that creates sugar molecules Carbon atoms from carbon dioxide are “fixed” when they are built into organic molecules that form three-carbon sugars These sugars are used to make glucose or are recycled to initiate the Calvin cycle again Two types of Photosynthetic Process Oxygenic Photosynthesis ➔ Light energy transfers electrons from water to carbon dioxide to produce carbohydrates ➔ The carbon dioxide is “reduced” or receives electrons ➔ The water becomes “oxidized” or loses electrons ➔ Oxygen is produced along with carbohydrates ➔ Most common and is seen in plants, algae, and cyanobacteria ➔ Basically functions as a counterbalance to respiration by taking in the carbon dioxide and reintroducing oxygen to the atmosphere Chemical equation: 6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O 6 molecules of carbon dioxide with 12 molecules of water using light energy yields to glucose with 6 molecules of oxygen and water Anoxygenic Photosynthesis ➔ Uses electron donors other than water ➔ What is produced depends on the electron donor Chemical equation: CO2 + 2H2A + Light Energy → [CH2O] + 2A + H2O Light-independent Reactions ● Dark reactions or Calvin Cycle ● Gets energy from the products of light dependent reaction (ATP and NADPH) ● Happens in the stroma How it goes: ➢ Has three chemical reactions steps: Carbon fixation Reduction Regeneration ➢ These reactions use water and catalysts Letter A is a variable and H2A represents the potential electron donor The Photosynthetic Apparatus Pigments ➔ Gives colors to plants ➔ Responsible for trapping sunlight ➔ Have different colors to absorb different wavelengths of light ● Types of pigments Chlorophylls ● Green colored ● Traps blue and red light ● Three subtypes (a, b, c) ● Chlorophyll A is found in photosynthesizing plants ● Mainly seen in purple and green bacteria (performs anoxygenic) Carotenoids ● ● ● Red, orange, or yellow Absorb bluish-green light Examples are xanthophyll (yellow) and carotene (orange) Phycobilins ● Red or blue ● Absorb wavelengths of light that are not well absorbed by the other two ● Seen in cyanobacteria and red algae Plastids ➔ Double-membraned plastids in plants and algae are called primary plastids while multiple-membraned found in plankton are secondary plastids ➔ Contains pigments or can store nutrients, responsible for making and storing food Types of plastids Chloroplasts ● Where photosynthesis occurs (grana and stroma) ● Have their own genome (collection of genes) contained within circular DNA These genes encode proteins essential to organelle and photosynthesis ● Converts to chromoplasts ● Gerontoplasts ● Chloroplasts that go with the ageing process, basically the chloroplasts that help convert into different other organelles when the leaf no longer undergoes photosynthesis (fall season) Leucoplasts ● Non-pigmented organelles (no color) ● Usually found in most of the non-photosynthetic pacers of the plant ● Acts as a storage shed for starches, lipids, and proteins depending on the need of the plants ● Mostly used for converting amino acids and fatty acids Three types Amyloplasts Store and synthesize starch Proteinoplasts Helps in storing the proteins that a plant needs Typically found in seeds Elaioplasts Helps in storing fats and oils that are needed by the plant Antennae ➔ Large collection of 100 to 5,000 pigment molecules ➔ Can effectively capture light energy from the sun, in the form of photons Notes ● Grana Stroma - Innermost portion of organelle Collection of disc-shaped membranes = individual discs are the thylakoids Empty spaces between columns of grana Chromoplasts ● Area for all the pigments to be kept and synthesized in the plant Can usually be found in flowering plants, ageing leaves and fruits Have carotenoid pigments ● The light energy must be transferred to a pigment-protein complex that can convert it into chemical energy in the form of electrons example , implants light energy is transferred to chlorophyll pigments The conversion to chemical energy will happen when a chlorophyll pigment expels an electron that moves on to an appropriate recipient Reaction Centers ● Pigments and proteins which convert light energy to chemical energy and begin the process of electron transfer
